Previously, a pair of superimposed rotary dies with cutting blades on one or both dies have been used to cut blanks from a thin web of material passing between the dies. Typically, the thin web is of a material such as paper, paperboard, cardboard, plastic film, metal foil, thin sheet metal, and the like. Such material may be received on a large roll and substantially continuously fed between the rotating dies to provide a relatively high rate of production of cut blanks from the web of material.
U.S. Pat. No. 4,608,895 discloses a pair of rotary die cylinders with integral complementary cutting blades thereon which coact to sever a web of material passing between the dies. While these die cylinders can be shifted both axially and in rotational phase relation with respect to each other to enable proper registration of the co-acting cutting blades to cut a web, the process to properly register the die cylinders is complicated and time consuming.
Generally, a soft, "putty-like" material is placed on each die cylinder so that upon rotation of the die cylinders, the cutting blades of each cylinder would form an impression in the putty on the opposed cylinder to enable an operator to determine the extent to which the die cylinders are offset and/or out of phase. From this, the dies are adjusted axially or in rotational phase relative to each other to properly align the cutting blades of each die cylinder. Preferably, after each such adjustment, additional putty is placed on each die cylinder and an impression in the putty is obtained by rotating the cylinders to ensure proper alignment of the rotary dies. This procedure is repeated until the proper registration or alignment of the rotary dies is achieved. Further adjustments may also be necessary if the center line or axis of rotation of the rotary dies are not parallel or are skewed relative to each other. In this case, one or both of the rotary dies must be shimmed or otherwise adjusted to provide for parallel axes of rotation of the rotary dies. Such adjustments also require the placement of putty on the rotary dies to insure that the adjustments have placed the rotary dies in the proper registration relative to each other. Obviously, this labor intensive, empirical adjustment process is rather complex and time consuming and increases the time to initially set up a machine, and to change one or both of the rotary dies and hence increases the downtime of the machine.